Tracheal mite, Acarapis woodi (Rennie) biology and ecology in the honey bee, Apis mellifera L

Abstract

The biology and ecology of the honey bee tracheal mite, Acarapis woodi (Rennie) were examined in a series of investigations. Mite reproduction was examined from cohorts of infested honey bees of known age dissected at regular intervals over four seasons. Duration of mite reproduction paralleled host longevity. Mites reproduced and progeny dispersed over a short duration (35 days) prior to the death of short lived bees (<40 days) in spring and summer. Longer lived winter bees harbored immature mites for the majority of the 120 days over which they were sampled. Numbers of mites peaked when bees were ca. 24 days old regardless of eventual host longevity. Oviposition by daughter females within the same host was revealed. A model of mite reproduction was developed to evaluate hypotheses of a second, or partial second generation of mites. The hypothesis of a complete second generation was supported when bees were infested with a low initial foundress mite population (one mite/bee), and lived 45-80 days. The alternative hypothesis of a partial second generation was supported by data from short lived bees, in which oviposition by daughters was limited. No oviposition by daughters was apparent when more than 2-3 foundress mites occupy a tracheal tube. Two foundress mites per tracheae may be the maximum for optimal reproduction. Resource deterioration limiting mite reproduction may involve physiological aging of the host, deterioration of the tracheal wall from mite feeding, or other unknown factors. The effects of methoprene (a mimic of host juvenile hormone) on mite reproduction were examined and no effects were evident. Dispersal by mated foundress's daughters to new host bees was a random process. Mite dispersals at night were eight times greater than corresponding daytime mite dispersals. No increases in daytime mite dispersals were observed when comparing confined and free flying infested bees of foraging age from the same colony. Host bees were physically less active at night, perhaps influencing the nocturnal dispersal pattern of mites. Mean flight times of infested and uninfested worker bees were not significantly different. The longevity of infested worker bees was slightly less than uninfested siblings.